Mexican flea cancer
| Mexican flea cancer | ||||||||||||
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Mexican flea cancer |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Hyalella azteca | ||||||||||||
| Saussure , 1858 |
The Mexican flea shrimp ( Hyalella azteca ) is a species native to North and Central America , or a complex of species, the flea shrimp . Numerous cryptospecies are summarized under this name , which are genetically and partly ecologically clearly distinguishable, but are currently not morphologically differentiated from one another. These are, with the exception of Hyalella azteca currently as species not formally described Service. Hyalella azteca s. st. has been described from Mexico, it is unclear to what extent animals from North America belong to it. Numerous old reports of the species for South America refer to other species of the genus Hyalella , which at that time were not yet differentiated.
features
The Mexican flea shrimp is a relatively small species with the typical body shape of the flea shrimp, males reach eight millimeters, females six millimeters in length. It can be distinguished from species of the suborder Gammaridea (with the large genus Gammarus ) by the relatively short first antennae, which are roughly the same length as the second antennae and lacking the small, accessory flagellum, and also by the missing palpus of the mandibles and the one-unit, accessory palpus of the first maxilla . The palpus of the maxillipede is five-segmented, with a long and slender terminal segment. The first two to three segments of the pleon have a distinct tooth on the top. The trunk section ( peraeon ) bears large coxal plates, which are thorn on the lower edge. The telson is rounded at the end, not cut or split, and has two large spines. The species is difficult to distinguish from other species of the genus, also outside of the Hyalella azteca species complex, and can be distinguished from the detailed features of the bristles ( chaetotaxia ), the proportions of the antennae and the proportions of certain limbs such as parts of the mouthparts and the urosomes.
habitat
The Mexican amphipod is widespread in lakes and rivers in North America, its range extends in northern Canada to the tree line. It is regarded as an indicator of water pollution, but its oxygen requirement is significantly lower than that of the native river flea shrimp. In South America it is caused by other species, e.g. B. represented Hyalella armata from Lake Titicaca .
In Europe there is so far no reliable evidence in the wild, although according to unconfirmed reports the species has lived in garden ponds for several years and also winters here. Because they are kept as aquarium and laboratory animals, introduction in the next few years is not considered unlikely.
Its diet consists mainly of vegetable detritus (e.g. fallen leaves ), and other food sources such as algae and carrion are also used opportunistically .
Cryptic speciation
The collective species Hyalella azteca s. l. According to analyzes of the DNA, consists of several, morphologically mostly indistinguishable, small species or crypto-species. Although it has not yet been possible to determine these according to morphological characteristics, in some cases it has been possible to identify differences in ecology and lifestyle. In several lines of development in habitats with strong predation by sunfish of the genus Lepomis, particularly small morphs have emerged, which fish are less fond of eating, while the animals become larger in fish-free habitats. Other crypto-species are spatially mixed in on lake shores, depending on the depth and distance from the shore.
Aquaristics
The Mexican flea shrimp was introduced into the home aquarium with supplies of ornamental fish and has since been bred as a food animal or for invertebrate aquariums because of its ease of keeping and maintenance.
Individual evidence
- ^ ER Gonzalez & Les Watling (2002): Redescription of Hyalella Azteca from Its Type Locality, Vera Cruz, Mexico (Amphipoda: Hyalellidae). Marine Sciences Faculty Scholarship. Paper 101. online
- ↑ Thomas Ols Eggers & Andreas Martens (2004): Additions and corrections to the "Identification key of the freshwater Amphipoda (Crustacea) of Germany". Lauterbornia 50: 1-13.
- ^ JDS Witt & PDN Hebert (2000): Cryptic species diversity and evolution in the amphipod genus Hyalella in central glaciated North America: a molecular phylogenetic approach. Canadian Journal of Fisheries and Aquatic Sciences 57: 687-698.
- ↑ JDS Witt, DL Threloff, PDN Hebert (2006): DNA barcoding reveals extraordinary cryptic diversity in an amphipod genus: implications for desert spring conservation. Molecular Ecology 15: 3073-3082. doi : 10.1111 / j.1365-294X.2006.02999.x
- ^ Gary A. Wellborn, Rickey Cothran, Suzanne Bartholf (2005): Life history and allozyme diversification in regional ecomorphs of the Hyalella azteca (Crustacea: Amphipoda) species complex. Biological Journal of the Linnean Society 84: 161-175.
- ^ Gary A. Wellborn & Rickey D. Cothran (2007): Niche diversity in crustacean cryptic species: complementarity in spatial distribution and predation risk. Oecologia 154: 175-183. doi : 10.1007 / s00442-007-0816-x